The present invention relates to metering equipment for metering fluid flow through an injector valve, comprising metering means and locating means arranged to locate such a valve in fluid communication with the metering means.
Such metering equipment is described in GB-A-2233101, in which a diesel engine injection pump injects fluid into a measuring chamber via an injection nozzle, whereby the volumes of successive injections can be measured.
One problem encountered by such metering equipment is the effect of the measuring chamber on the metering.
The present invention seeks to obviate this disadvantage.
Accordingly, the present invention is directed to metering equipment according to the opening paragraph of the present specification, in which the metering means are upstream of the locating means.
Rapid and accurate metering of fluid flow through the injector valve is thereby made possible.
An advantage of such a construction is that the injector valve is itself used to drain fluid from the metering means.
Preferably, the metering equipment is for metering the fluid flow through a solenoid-operated petrol injection valve.
In an especially advantageous embodiment of the present invention, the metering equipment is volumetric metering equipment, and the metering means measure the volume of one or more injections through the injector valve.
The metering means may be so constructed as to act as a pump to cause the flow of fluid through the injector valve. This may be achieved especially effectively if the metering means are in the form of a piston and cylinder arrangement such that the cylinder provides a measuring chamber and linear movement of the piston is indicative of the volume of fluid which flows through the valve. The piston may have a relatively low cross-sectional area to give a relatively large movement for a given flow throughput.
Advantageously a source of fluid under pressure is connected to the measuring chamber side of the piston. A further source of fluid under pressure may be connected to a chamber on the other side of the piston. The fluid from this further source may be gaseous, to act more effectively as a spring urging the piston towards the valve when the equipment is in use whilst still maintaining pressure within a predetermined range, although it may be oil.
The equipment may further comprise a magnetic induction device, or a linear variable differential transformer or a diffraction grating or other optical device, to provide a measure of the linear movement of the piston, and such measuring means may be external to the chamber.
The equipment may be provided with control means to effect an injection operation of the valve. Also the equipment may have adjustment means to adjust the valve, and it may have programmable or hard-wired servo loop means to adjust the valve until the volume of an injection as measured by the equipment is within a predetermined range.
The equipment may further comprise crimping means to crimp the valve, and thus fix it with the given adjustment, once that volume is within that range.
The present invention extends to a method of metering fluid flow through an injector valve in which fluid flow upstream of the valve is metered.